We propose to extend our studies of indices of central dopaminergic activity during chronic antipsychotic drug administration in animals and man. We will measure plasma DOPAC and HVA, CSF GABA, and regional brain HVA in rabbits following acute and chronic treatment with haloperidol or thioridazine. We will also measure plasma HVA and DOPAC, serum prolactin, CSF HVA, prolactin, GABA and cAMP in patients treated with haloperidol or thioridazine. We will be examining patterns of tolerance and correlations with symptom change in our clinical studies.